However, Woolworths' social media manager clearly hadn't done their research before posting the message, as instead of mentioning the new Olympic champion, they tagged a different Kyle Chalmers, who is in fact a a 19-year-old trainee radio communication technician from Scotland.

Australian Chalmers won gold in the 100m freestyle event in Rio (Image: AFP/Getty)

He is Australia's youngest male swimming gold medalist for 16 years (Image: AFP/Getty)

After lapping up the congratulatory messages from a number of other users, he issued a tweet declaring himself "too fat" to swim.

The Scot wrote: "So apparently I've just won a gold medal!!! Get in there! Great way to wake up! #wrongkyle #IDontSwimImTooFat."

Woolworths have since realised their mistake and posted the following ingenious tweet in an expert way to save their blushes.

The real Kyle Chalmers (well, the swimmer who won the gold medal) made history in doing so as he became the first Australian to finish first in the 100m freestyle event since Mike Wenden in 1968.

He is also the youngest male Australian swimmer to win an Olympic gold medal since a 17-year-old Ian Thorpe won three golds at the Sydney Games in 2000.

Chalmers holds up his gold medal on the podium after the race (Image: AFP/Getty)